First, there are a few little problems having to do with the human eye.

1. Ultraviolet is not the best stuff to expose your eyes to. Furthermore, at
least one damage mode may be affected by peak exposure intensity, even for a
given amount of average exposure intensity. Many UV-A wavelengths are believed
to contribute to "nuclear cataracts", which is a permanent brown discoloration of
the central portions of the lens of the eye. The damage requires affected
molecules to receive at least two photons, and to receive the second one before
it recovers from the first. Damage may therefore be some function of peak and
average exposure intensity. You need your eyes to get no more UV than a fraction
of what you would get from natural daylight.

1a. In dark/dim areas, the pupils of peoples' eyes get big, and are big
when the strobe goes off.

2. It is the central regions of the lens that most attenuate lower-visibility
deep violet and borderline UV wavelengths. With the pupils being more dilated
from darkness between flashes, the thinner edges of the lens let you see more
of some of the wavelengths used for the "blacklight" effect. With this light
being more visible than usual, the "blacklight" effect is not as
apparent.

3. Human vision often sees contrast less with strobe lights than with steady
lights. This can reduce the apparent brightness of fluorescent objects
illuminated by a strobe blacklight.

But if you want to try to make a blacklight strobe anyway, here is a way
to make a small one using the glass bulb of a "blacklight" bulb.
Please note that these bulbs let out some visible violet and blue
light and may not look very dark when used.

NOTE: The bulb-butchery mentioned below may require practice, and you may want
to practice this on 80-cent regular bulbs before doing it with $3-$4 blacklight bulbs.

CAUTION: The below method requires butchering a glass bulb, which has
obvious hazards. Do so only if and when and where it is tolerable to spew
out a few bits of glass. Use of safety goggles and gloves is recommended.

Get a 75 watt "blacklight" bulb, needlenose plyers, a flat-blade screwdriver,
and a pair of diagonal cutters that you don't mind treating roughly.

1. Remove the metal contact from the bottom of the base of the bulb.

2. Break out the piece of glass that separates the above contact from
the main part of the base of the bulb. This may require alternating
between different tools.

3. Use the diagonal cutters to peel off the lower portion of the
siding of the base, almost up to the cement inside the base.

4. This gets a bit tricky. Use the pliers or the cutters to break the
exhaust tip in the bottom of the bulb, if this stem is still intact. Break
off/out the portion of glass around this, making a large enough hole. You
may have to break off/out a portion of the cement.

5. Get the stem assembly out of the bulb. There may be a heat shield which
you may have to bend somehow before it will come out through the hole in the
bottom of the bulb. Be sure the hole is big enough to get your flashtube in.

Now that you have an empty blacklight bulb with a hole in the bottom, put
a flashtube into the bulb. Seal with silicone rubber if you want to make
it permanent, but poke or drill a hole in the silicone (or in any other
way be sure this is NOT airtight). You don't want a possibly weakened
glass bulb to be pressurized if/when it heats up.

Another idea: Cut a length of dark violet glass tubing from a fluorescent
style blacklight tube. This works better. For some more details, go to my
Blacklight Tube Hacking File. You will probably
want to set up a hot wire type glass tube cutter. Otherwise, just put the
flashtube in a whole blacklight tube. You are probably better off leaving
the phosphor coating in place, unless you have reasons for NOT having the
light diffused such as for focusing it into a beam.

As for how to make this make as much "blacklight" as easily possible: Use a
quantity of flash energy near half the maximum the flashtube will take, with
the maximum voltage that the flashtube is rated for. You can probably get away
with a bit of extra voltage. You may want to select a capacitor for extra
voltage; many won't take over 330 volts and you probably want to try getting
away with a little more for a small camera flash or strobe flashtube.
If the energy quantity is lower, the ideal voltage is less certain. Higher
voltage favors a slight spectral shift towards UV, but smaller capacitance
favors a line spectrum that largely lacks "blacklight" UV lines. If you have
a spectroscope or a diffraction grating, you want the smallest capacitance
and highest voltage that gives you mostly a continuous spectrum instead of
spectral lines. If you use low capacitance and high voltage and must
deal with a line spectrum, then it is probably best to go for really high
voltage, which favors a violet and violet-blue cluster of spectral lines,
which has some "blacklight" effect. Most non-blue fluorescent paints,
inks, and dyes fluoresce from violet and blue visible light.
Small straight flashtubes made for cameras seem better for producing
longwave UV than the popular U-shaped strobe tube. The U-shaped strobe
tube more easily produces a line spectrum unless you have very high
capacitance of at least several hundred microfarads. Also, camera flash tubes
can easily fit into a 4 watt blacklight fluorescent tube.

Quartz xenon flashlamps generally favor higher xenon plasma temperature that
favors more UV output. Also, quartz flashtubes (other than ones of varieties
doped or coated for blocking UV) are more transparent to UV in or near the
UVB and UVC ranges than glass flashtubes are. Then again, glass flashtubes
and protective glass used with many quartz flashtubes pass most of the UVA
range of ultraviolet, which is more useful for achieving "blacklight effects"
and less dangerous than UVB and UVC.

One thing to consider is a "capacitance rule" that I have become aware of,
for getting a xenon flashlamp to be a good blackbody/graybody emitter of a
continuous spectrum including UV. Please note that there are also requirements
for quantity of energy in the energy storage capacitor(s) and voltage that
the energy storage capacitor(s) must be charged to in order to achieve good
efficiency of a xenon flashlamp's production of UV.

The capacitance rule that I have noticed: It is necessary for the energy
storage capacitor(s) to have capacitance of about or more than .15 farad,
divided by the xenon pressure in torr, multiplied by the square of the
flashtube's inside diameter (bore) in mm, divided by the flashtube's arc
length in mm.

When the xenon pressure is close to or above the 450 torr typical of most quartz
linear flashlamps of kinds used for pumping lasers, I have found that 10% less
capacitance than recommended above works well. This means with 450 torr: Use at
least about 300 microfarads, times the square of the flashtube's inside / bore
diameter in mm, divided by the arc length in mm.

Another thing I have found: Achieving this amount of capacitance combined with
a specific percentage of the flashlamp's "explosion energy" (often recommended
to not exceed 30%), favors flashtubes with smaller inside / bore diameter.

The narrowest/smallest interior/bore diameter quartz xenon flashlamps that are
reasonably common have this bore diameter being 4 millimeters. This means that
my "capacitance rule" predicts that with most quartz xenon flashlamps with
inside diameter 4 mm, outside diameter 6 mm, the capacitance required to achieve
good broadband continuous spectrum including UV is 4800 microfarads divided by
the flashlamp's arc length in millimeters. Flash durations around or a little
over 100 microseconds are favorable for quartz flashlamps with bore diameter
4 mm (and xenon pressure of 450 torr) to be used with 20-30 % of their
"explosion energy" with the minimum recommended capacitance and an appropriate
series inductor. A conservative estimate of the "single pulse explosion energy"
of a quartz flashlamp is 3.5 joules times the flashlamp's bore diameter in
millimeters times its arc length in millimeters times the square root of the
flash duration in milliseconds. There are higher figures as high as 7.78 joules
times the arc length in millimeters, times the bore diameter in millimeters,
times the square root of the flash duration in milliseconds in a critically
damped circuit with an inductor, with xenon pressure of 450 torr, for high
quality quartz linear flashlamps with bore diameter 8 mm or less.

Lamp life expectancy is typically around 27,000 flashes at 30% of the explosion
energy, around 130,000 flashes at 25% of the explosion energy, and around
800,000 flashes at 20% of the explosion energy, according to a "one size fits
all" formula. Actual life may be less due to peak current density exceeding
4,000 amps per square centimeter of arc cross section. Also, external triggering
may cause or contribute to life being shorter than predicted by leading to an
uncentered arc. On the other hand, when these percentages are percentages of the
conservative 3.5 joules times bore diameter in mm times arc length in mm times
the square root of flash duration in milliseconds, these life expectancies may
be realistic.

Table for flashlamps with 4 mm bore diameter
Capacitance is 4800 uF divided by the arc length in millimeters

Note: Usage of switching means to control flash duration is a separate issue
with different equations, and generally incompatible with the scheme of series
inductors historically used to maximize performance of quartz xenon
flashlamps.)